In vehicular delay tolerant networks (VDTNs), multicast has been increasingly popular due to new applications, among which large contents such as multimedia files play a major role. Under this circumstance, existing works have failed to provide efficient solutions. To tackle this challenge, in this paper, we introduce data coding into throwbox-based system architecture and propose the optimal coding option scheme under the constraints of memory space. Finally, two data forwarding algorithms are designed. One is applied when data being forwarded from a vehicle to another. The other runs in throwboxes and is used to forward data to vehicles. The extensive trace-driven simulation demonstrates that the proposed method produces shorter delay and higher success rates in comparison with two baseline routing algorithms in VDTNs.INDEX TERMS Opportunistic coding, throwbox, multicast, vehicular delay tolerant network, large content.